1. Field of the Invention
The present invention relates to a rotary machine life expectancy prediction method, which measures life expectancy of a rotary machine, and a rotary machine repair timing determination method, which determines most appropriate repair timing for a rotary machine based on the life expectancy thereof.
2. Description of the Related Art
Failure diagnosis has become important for the sake of efficient semiconductor device manufacturing. Especially as the trend towards large item/small volume production of system LSI grows, an efficient yet highly adaptable semiconductor device manufacturing method has become necessary. It is possible to use a small-scale production line for efficient production of semiconductor devices. However, if the production line is merely reduced, the capacity utilization of manufacturing equipments drops. Accordingly, there are problems such as investment efficiency falling in comparison with large-scale production lines. To rectify this situation, there is method where a plurality of manufacturing processes is performed on one semiconductor manufacturing equipment. For example, in a low-pressure chemical vapor deposition (LPCVD) system, reactive gases introduced and reaction products differ depending on the types of film depositions. These are evacuated from the LPCVD chamber using a vacuum pump. Accordingly, the film deposition requirements differ and the formation situations for reaction products within the vacuum pump differ depending on the types of manufacturing process. Therefore, life expectancy of the vacuum pump is affected by the process history.
Normally, sensors for monitoring currents, temperatures, etc. during operation are attached to the vacuum pump. By doing so, whether a vacuum pump is malfunctioning can be observed by an operator, either by directly viewing them or from information on plotted graphs. However, since the currents and the temperatures change for the vacuum pump depending on the various process conditions, it is extremely difficult to measure life expectancy of the vacuum pump from these values, which change with every process.
If the vacuum pump should have an irregular shutdown during film deposition in LPCVD, then the lot being processed becomes defective. Moreover, excessive maintenance of the LPCVD system may become necessary due to microscopic dust caused by residual reactive gases, within the chamber and the piping used for gas introduction or vacuum evacuation. Implementation of such excessive maintenance causes manufacturing efficiency of the semiconductor device to drop dramatically.
If regular maintenance is scheduled with a margin of safety as a measure to prevent such sudden irregular shutdowns during the manufacturing process, the frequency for maintaining the vacuum pump may become astronomical. Not only does this increase maintenance cost, but it also invites a decrease in capacity utilization of the LPCVD system due to changing the vacuum pump, causing the manufacturing efficiency of the semiconductor device to drastically decline. To commonly use semiconductor manufacturing equipment for a plurality of processes, which is required for an efficient small-scale production line, it is desirable to accurately diagnose vacuum pump life expectancy and to operate the vacuum pump without having any waste in terms of time.
Previously, some methods of diagnosing vacuum pump life expectancy have been proposed. In Japanese Patent Application Laid-open No. 2000-283056, vacuum pump failure forecasting using a plurality of physical quantities such as amount of current, temperature or vibration for the vacuum pump is disclosed. In addition, it has been disclosed that operating conditions of the semiconductor manufacturing equipment such as operating time versus stand-by time must be considered to forecast vacuum pump failure. However, it is impossible for this to accommodate historical results of vacuum pump life expectancy in the case where a common semiconductor manufacturing equipment is used for a plurality of processes. It is noted that the objective of Japanese Patent Application Laid-open No. 2000-283056 lies in observing abnormalities of a vacuum pump, and not in forecasting life expectancy. Therefore, demands have been made for development of an apparatus and method for predicting vacuum pump life expectancy.